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regsub.c revision 1.3 
      1 /*
      2  * regsub
      3  *
      4  *	Copyright (c) 1986 by University of Toronto.
      5  *	Written by Henry Spencer.  Not derived from licensed software.
      6  *
      7  *	Permission is granted to anyone to use this software for any
      8  *	purpose on any computer system, and to redistribute it freely,
      9  *	subject to the following restrictions:
     10  *
     11  *	1. The author is not responsible for the consequences of use of
     12  *		this software, no matter how awful, even if they arise
     13  *		from defects in it.
     14  *
     15  *	2. The origin of this software must not be misrepresented, either
     16  *		by explicit claim or by omission.
     17  *
     18  *	3. Altered versions must be plainly marked as such, and must not
     19  *		be misrepresented as being the original software.
     20  */
     21 
     22 #ifndef lint
     23 static char *rcsid = "$Id: regsub.c,v 1.3 1993/08/26 00:45:37 jtc Exp $";
     24 #endif /* not lint */
     25 
     26 #include <regexp.h>
     27 #include <stdio.h>
     28 #include <string.h>
     29 #include "regmagic.h"
     30 
     31 #ifndef CHARBITS
     32 #define	UCHARAT(p)	((int)*(unsigned char *)(p))
     33 #else
     34 #define	UCHARAT(p)	((int)*(p)&CHARBITS)
     35 #endif
     36 
     37 /*
     38  - regsub - perform substitutions after a regexp match
     39  */
     40 void
     41 regsub(prog, source, dest)
     42 const regexp *prog;
     43 const char *source;
     44 char *dest;
     45 {
     46 	register char *src;
     47 	register char *dst;
     48 	register char c;
     49 	register int no;
     50 	register int len;
     51 	extern char *strncpy();
     52 
     53 	if (prog == NULL || source == NULL || dest == NULL) {
     54 		regerror("NULL parm to regsub");
     55 		return;
     56 	}
     57 	if (UCHARAT(prog->program) != MAGIC) {
     58 		regerror("damaged regexp fed to regsub");
     59 		return;
     60 	}
     61 
     62 	src = (char *)source;
     63 	dst = dest;
     64 	while ((c = *src++) != '\0') {
     65 		if (c == '&')
     66 			no = 0;
     67 		else if (c == '\\' && '0' <= *src && *src <= '9')
     68 			no = *src++ - '0';
     69 		else
     70 			no = -1;
     71  		if (no < 0) {	/* Ordinary character. */
     72  			if (c == '\\' && (*src == '\\' || *src == '&'))
     73  				c = *src++;
     74  			*dst++ = c;
     75  		} else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
     76 			len = prog->endp[no] - prog->startp[no];
     77 			(void) strncpy(dst, prog->startp[no], len);
     78 			dst += len;
     79 			if (len != 0 && *(dst-1) == '\0') {	/* strncpy hit NUL. */
     80 				regerror("damaged match string");
     81 				return;
     82 			}
     83 		}
     84 	}
     85 	*dst++ = '\0';
     86 }
     87